Replaceable cutting head having back-tapered conical external thread and rotary cutting tool

Abstract

A rotary cutting tool includes a replaceable cutting head and a tool holder. The replaceable cutting head includes a forward cutting portion and a rearward mounting portion. The mounting portion includes a male coupling member that includes a back-tapered conical external thread. The tool holder includes a female coupling member that includes an internal thread. When the rotary cutting tool is in a locked position, the external thread is threadingly engaged with the internal thread.

What is claimed is: 
     
       1. A replaceable cutting head ( 22 ), having a head longitudinal axis (A) extending in a forward (D F ) to rearward direction (D R ), comprising
 a forward portion forming a cutting portion ( 26 ); and 
 a rearward portion forming a mounting portion ( 28 ), the mounting portion ( 28 ) comprising a male coupling member ( 38 ) having an external thread ( 42 ) and protruding rearwardly from a head base surface ( 40 ), the head base surface ( 40 ) extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion ( 26 ) and the mounting portion ( 28 ), wherein:
 the external thread ( 42 ) comprises an external thread ridge ( 44 ) extending helically about an external thread axis (B) and comprising forward and rearward external flank surfaces ( 46 ,  48 ) and an external top surface ( 50 ) extending therebetween; 
 the forward and rearward external flank surfaces ( 46 ,  48 ) generally face in opposite axial directions (D F , D R ) and delimit a helical external thread groove ( 52 ) that comprises an external bottom surface ( 54 ); 
 the external thread ( 42 ) of the male coupling member ( 38 ) is a back-tapered conical thread having at least one thread diameter (d 1 , d 2 ) which increases in the rearward direction (D R ); 
 at least one of the external thread ridge ( 44 ) and the external thread groove ( 52 ) extends about a respective cone (K 1 , K 2 ) having a cone angle (γ); and 
 the cone angle (γ) is in the range of 0.4°≤γ≤1.0°. 
 
 
     
     
       2. The replaceable cutting head ( 22 ) according to  claim 1 , wherein both the external thread ridge ( 44 ) and the external thread groove ( 52 ) extend about a respective cone (K 1 , K 2 ), an outer cone (K 2 ) and an inner cone (K 1 ), respectively. 
     
     
       3. The replaceable cutting head ( 22 ) according to  claim 2 , wherein the cone angle (γ) is the same for the inner cone (K 1 ) and the outer cone (K 2 ). 
     
     
       4. The replaceable cutting head ( 22 ) according to  claim 1 , wherein in a cross-sectional view taken in an axial plane containing the external thread axis (B):
 the external top surface ( 50 ) forms a plurality of external thread crests ( 56 ) that are sloped with respect to the external thread axis (B) and co-linear with each other; and 
 the external bottom surface ( 54 ) forms a plurality of external thread roots ( 58 ) that are sloped with respect to the external thread axis (B) and co-linear with each other. 
 
     
     
       5. The replaceable cutting head ( 22 ) according to  claim 1 , wherein in a cross-sectional view taken in an axial plane containing the head longitudinal axis (A), the external thread ( 42 ) defines an external thread form ( 60 ) that is trapezoidal. 
     
     
       6. The replaceable cutting head ( 22 ) according to  claim 1 , wherein the external thread ( 42 ) has a constant external thread pitch (PE). 
     
     
       7. A rotary cutting tool ( 20 ) having a longitudinal axis (L) and extending in a forward (D F ) to rearward direction (D R ), comprising:
 a tool holder ( 24 ) having a holder longitudinal axis (C) and comprising a female coupling member ( 68 ) having an internal thread ( 72 ) extending rearwardly from a holder forward surface ( 70 ), the holder forward surface ( 70 ) extending transversely with respect to the holder longitudinal axis (C); and 
 a replaceable cutting head ( 22 ) threadingly engaged to the tool holder ( 24 ), the replaceable cutting head ( 22 ) having a head longitudinal axis (A) extending in a forward (D F ) to rearward direction (D R ), and comprising 
 a forward portion forming a cutting portion ( 26 ); and 
 a rearward portion forming a mounting portion ( 28 ), the mounting portion ( 28 ) comprising a male coupling member ( 38 ) having an external thread ( 42 ) and protruding rearwardly from a head base surface ( 40 ), the head base surface ( 40 ) extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion ( 26 ) and the mounting portion ( 28 ), wherein:
 the external thread ( 42 ) comprises an external thread ridge ( 44 ) extending helically about an external thread axis (B) and comprising forward and rearward external flank surfaces ( 46 ,  48 ) and an external top surface ( 50 ) extending therebetween; 
 the forward and rearward external flank surfaces ( 46 ,  48 ) generally face in opposite axial directions (D F , D R ) and delimit a helical external thread groove ( 52 ) that comprises an external bottom surface ( 54 ); and 
 the external thread ( 42 ) of the male coupling member ( 38 ) is a back-tapered conical thread having at least one thread diameter (d 1 , d 2 ) which increases in the rearward direction (D R ); 
 
 wherein: 
 the rotary cutting tool ( 20 ) is adjustable between:
 a released position in which the internal and external threads ( 42 ,  72 ) are not threadingly engaged to one another, and 
 a locked position in which the male coupling member ( 38 ) is removably retained in the female coupling member ( 68 ) with the internal and external threads ( 42 ,  72 ) threadingly engaged to one another; and 
 
 the frictional engagement between the external thread ( 42 ) and the internal thread ( 72 ) increases in a direction from a forwardmost turn of the external thread ( 42 ) towards the rearmost turn of the external thread ( 42 ). 
 
     
     
       8. The rotary cutting tool ( 20 ) according to  claim 7 , wherein the internal thread ( 72 ) of the female coupling member ( 68 ) is a straight thread. 
     
     
       9. The rotary cutting tool ( 20 ) according to  claim 7 , wherein:
 the internal thread ( 72 ) comprises an internal thread ridge ( 74 ), extending helically about an internal thread axis (D), and comprising forward and rearward internal flank surfaces ( 76 ,  78 ) and an internal top surface ( 80 ) extending therebetween; 
 the forward and rearward internal flank surfaces ( 76 ,  78 ) generally face in opposite axial directions (D F , D R ) and delimit a helical internal thread groove ( 82 ) that comprises an internal bottom surface ( 84 ); and 
 the forward external flank surface ( 46 ) and the forward internal flank surface ( 76 ) face in the forward direction (D F ); 
 the rearward external flank surface ( 48 ) and the rearward internal flank surface ( 78 ) face in the rearward direction (D R ); and 
 in the locked position, the rearward internal flank surface ( 78 ) abuts the forward external flank surface ( 46 ). 
 
     
     
       10. The rotary cutting tool ( 20 ) according to  claim 9 , wherein in the locked position:
 the forward internal flank surface ( 76 ) is spaced apart from the rearward external flank surface ( 48 ) by a rearward flank distance (D 1 ); 
 the internal top surface ( 80 ) is spaced apart from the external bottom surface ( 54 ) by an upper distance (D 2 ); and 
 the internal bottom surface ( 84 ) is spaced apart from the external top surface ( 50 ) by a lower distance (D 3 ). 
 
     
     
       11. The rotary cutting tool ( 20 ) according to  claim 7 , wherein the internal thread ( 72 ) has a constant internal thread pitch (PI) which is the same as a constant external thread pitch (PE) of the external thread ( 42 ). 
     
     
       12. The rotary cutting tool ( 20 ) according to  claim 7 , wherein:
 at least one of the external thread ridge ( 44 ) and the external thread groove ( 52 ) extends about a respective cone (K 1 , K 2 ) having a cone angle (γ); and 
 the cone angle (γ) is in the range of 0.02°≤γ≤1.0°. 
 
     
     
       13. The rotary cutting tool ( 20 ) according to  claim 7 , wherein:
 at least one of the external thread ridge ( 44 ) and the external thread groove ( 52 ) extends about a respective cone (K 1 , K 2 ) having a cone angle (γ); and 
 the cone angle (γ) is in the range of 0.4°≤γ≤1.0°. 
 
     
     
       14. A rotary cutting tool ( 20 ) having a longitudinal axis (L) and extending in a forward (D F ) to rearward direction (D R ), comprising:
 a replaceable cutting head ( 22 ) having a head longitudinal axis (A) extending in said forward (D F ) to rearward direction (D R ), and comprising:
 a forward portion forming a cutting portion ( 26 ); and 
 a rearward portion forming a mounting portion ( 28 ), the mounting portion ( 28 ) comprising a male coupling member ( 38 ) having an external thread ( 42 ) and protruding rearwardly from a head base surface ( 40 ), the head base surface ( 40 ) extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion ( 26 ) and the mounting portion ( 28 ), wherein:
 the external thread ( 42 ) comprises an external thread ridge ( 44 ) extending helically about an external thread axis (B) and comprising forward and rearward external flank surfaces ( 46 ,  48 ) and an external top surface ( 50 ) extending therebetween; 
 the forward and rearward external flank surfaces ( 46 ,  48 ) generally face in opposite axial directions (D F , D R ) and delimit a helical external thread groove ( 52 ) that comprises an external bottom surface ( 54 ); and 
 the external thread ( 42 ) of the male coupling member ( 38 ) is a back-tapered conical thread having at least one thread diameter (d 1 , d 2 ) which increases in the rearward direction (D R ); and 
 
 
 a tool holder ( 24 ) having a holder longitudinal axis (C) and comprising:
 a female coupling member ( 68 ) having an internal thread ( 72 ) extending rearwardly from a holder forward surface ( 70 ), the holder forward surface ( 70 ) extending transversely with respect to the holder longitudinal axis (C); wherein: 
 the internal thread ( 72 ) comprises an internal thread ridge ( 74 ), extending helically about an internal thread axis (D), and comprising forward and rearward internal flank surfaces ( 76 ,  78 ) and an internal top surface ( 80 ) extending therebetween; and 
 the forward and rearward internal flank surfaces ( 76 ,  78 ) generally face in opposite axial directions (D F , D R ) and delimit a helical internal thread groove ( 82 ) that comprises an internal bottom surface ( 84 ); and 
 
 wherein:
 the rotary cutting tool ( 20 ) is adjustable between:
 a released position in which the internal and external threads ( 42 ,  72 ) are not threadingly engaged to one another, and 
 a locked position in which the male coupling member ( 38 ) is removably retained in the female coupling member ( 68 ) with the internal and external threads ( 42 ,  72 ) threadingly engaged to one another; and 
 
 in the locked position:
 the forward internal flank surface ( 76 ) is spaced apart from the rearward external flank surface ( 48 ) by a rearward flank distance (D 1 ); 
 the internal top surface ( 80 ) is spaced apart from the external bottom surface ( 54 ) by an upper distance (D 2 ); 
 the internal bottom surface ( 84 ) is spaced apart from the external top surface ( 50 ) by a lower distance (D 3 ); and 
 the rearward flank, upper and lower distances (D 1 , D 2 , D 3 ) all decrease in the rearward direction (D R ).